1. Field of the Invention
This invention relates generally to a high speed data storage disk drive, and more particularly to a disk drive having a vibration damper for more accurate data access at high speed rotation.
2. Background of the Invention
Data storage disks such as optical compact disks (CD) have become popular data storage media, being capable for storing large amounts of data at a relatively low cost per datum. A typical CD-ROM can store about 640 MBytes of data, and the new Digital Versatile Disks (DVD) can store more than 2.5 GBytes of data. A disk drive comprising a data pickup head is used to read data from the compact disks. The data pickup head must align precisely to the recording tracks of the compact disks to accurately read data.
A disadvantage of the optical disks has been the low data transfer rate of the disk drives. Earlier CD-ROM drives had a data transfer rate of about 150 KBytes/sec. By increasing the rotation speed of the optical compact disk, it is possible to increase the data transfer rate. Presently, 32xc3x97 speed CD-ROM drives have been developed. The 32xc3x97 speed CD-ROM drive is capable of rotating a disk at a speed which is thirty-two times the speed of a conventional audio CD. When a disk rotates at high speed, any imbalance on the disk itself will result in an increase in the vibration of the disk drive.
A perfect disk has its center of mass exactly at the geometrical center of the disk. Due to manufacturing errors, the center of mass of a CD-ROM disk typically vary by 0-6 g-mm from the center (where 1 g-mm equals to 1 gram of mass located 1 mm from center). This is tolerable for 16xc3x97 or slower speed CD-ROM drives. But for a 32xc3x97 or higher speed CD-ROM drive with a disk rotating at approximately 8000 rpm (revolutions per minute), the vibration due to an imbalance will likely result in reading errors arising from the inability of the data pick-up head to align precisely with the recording tracks on the disk. The vibration will also be translated to the housing of the CD-ROM drive, and further on to the computer housing, resulting in an annoying vibration noise of the drive unit.
One conventional method of reducing vibration is to use a heavy metal frame to stabilize the pickup head and data storage disk. As the disk drive speed increases, the weight of the base of the disk drive motor must also be increased. However, to reduce the vibration to an acceptable level, the weight required for a 33xc3x97 speed disk drive would be about 3 times the weight of normal disk drives.
Another method that has been proposed is to use vibration absorbers, such as soft rubber pads to absorb vibration. FIG. 1 shows a schematic drawing of the damping mechanism of a prior art disk drive comprising a center base and a retaining frame. The center base supports a motor and a data pickup head. The retaining frame is connected to an outer housing. Rubber pads are inserted between the retaining frame and the center base to absorb and reduce vibration (the details of the motor and pickup head are not shown).
Vibration absorbers with different damping coefficients have different vibration damping properties. Typically, soft rubber pads have been used to dampen high frequency vibration, whereas hard rubber pads are used to dampen low frequency vibration.
FIG. 2(a) show the vibration amplitude of the center base at different motor rotation frequencies when soft damping pads are used in a prior art disk drive. FIG. 2(b) show the vibration amplitude of the retaining frame at different motor drive frequencies when soft damping pads are used in a prior art disk drive (xe2x80x9cf0xe2x80x9d refers to the normal operation frequency of the disk drive). The soft damping pads are made from a material which will have a resonant frequency lower than the operation frequency of the motor drive. As can be seen, when soft damping pads are used, the vibration level of the retaining frame is greatly reduced, while the vibration amplitude of the center base remains quite high (a vertical scale of one corresponds to the vibration amplitude of a stand-alone center base (i.e., not coupled to the retaining frame) of a prior art disk drive operating at frequency f0).
FIG. 2(c) show the center base vibration amplitude versus motor drive rotation frequency curve when hard damping pads are used in a prior art disk drive. FIG. 2(d) show the retaining frame vibration amplitude versus motor drive rotation frequency curve when hard damping pads are used in a prior art disk drive. The hard damping pads are made from a material which will have a resonant frequency higher than the operation frequency of the motor drive. As can be seen, when hard damping pads are used, the vibration level of the center base can be reduced somewhat, while the vibration amplitude of the retaining frame becomes quite high.
As can be seen, using damping pads cannot satisfactorily reduce the vibration caused by high speed rotation of disks with center of mass located away from the geometrical center.
What is needed, therefore, is a method and device for reducing vibration of a high speed disk drive without unduly increasing overall weight.
The present invention is a disk drive for reading data from a data storage disk, the disk drive comprising a center base, a retaining frame, a vibration absorber, a first plurality of vibration transfer-dampers, and a second plurality of vibration transfer-dampers. The first plurality of vibration transfer-dampers, and a second plurality of vibration transfer-dampers. The center base supports the motor and the data storage disk. The retaining frame retains the vibration absorber and the center base. The first plurality of vibration transfer-dampers are coupled to the retaining frame and the vibration absorber for damping and transferring vibrations. The second plurality of vibration transfer-dampers are coupled to the center base and the vibration absorber, for transferring and damping vibrations of the center-base to the vibration absorber, thereby reducing the vibration of the center base.
One advantage of the present invention is to provide a cost-effective method of reducing vibration in high speed disk drives caused by disk imbalances, resulting in more reliable read/write operations.
Another advantage is that the vibration noise incurred on the outer housing is reduced, thereby lowering the vibration noise level during disk drive operation.